1. Field of the Invention
The present invention relates to an operating microscope with a main objective that extends along an objective plane and is penetrated by a binocular main observer beam path and a binocular co-observer beam path. Additionally, the invention relates to a method for pivoting a co-observer microscope around a main observer microscope.
2. Description of the Related Art
During surgery carried out with the aid of an operating microscope, it is often desirable, or even necessary, for an assistant of the treating surgeon to likewise be able to observe the operation site in an enlarged fashion through the operating microscope. It is for this reason that operating microscopes are often equipped with a binocular tube for an assistant, the so-called assistant tube or co-observer tube, also referred to as co-observer microscope, in addition to a binocular tube for the main observer, the so-called main observer tube or main observer microscope. Here each tube has its own stereoscopic beam path, wherein the stereoscopic beam paths both penetrate a common main objective. Operating microscopes for main and co-observer are for example distributed by the applicant under the name of OPMI and under the name of OPMI Lumera.
Decoupling the stereoscopic beam path for the co-observers can for example be brought about via physical beam splitters (e.g. partly reflecting mirror surfaces or prism surfaces without total reflection), which decouple part of the observation light intensity from the beam path of the main observer and couple it into the co-observer beam path. Operating microscopes in which physical beam splitters are used for decoupling the co-observer beam path are described in, for example, US 2006/0023300 A1, in DE 102 43 852 B4, DE 197 18 102 A1, DE 33 33 471 A1 and in DE 1 217 099. However, the use of a beam splitter for decoupling the co-observer beam path is afflicted by the disadvantage of neither the main observer nor the co-observer having the full intensity of the observer beam path, and hence the full image brightness, available to them. While this only plays a minor role in operations in which work can be undertaken with intensive illumination, the light loss for the main observer and co-observer cannot always be accepted in eye operations in particular. By way of example, in cataract operations, in which the lens of the eye is removed, a so-called red reflex is used to illuminate the lens during the operation. The red reflex is generated as a result of reddish to orange reflection of the illumination light on the retina. This type of lens illumination is of low intensity because, on the one hand, not all of the illumination light is reflected on the retina and, on the other hand, the illumination intensity on the retina may not be too high so as not to damage the latter. Light loss by beam splitting is therefore generally undesirable in ophthalmological operating microscopes.
In operating microscopes in which there should be no loss of brightness for the main observer and the co-observer, the decoupling of the co-observer beam path is brought about by mirroring surfaces (also referred to as geometric beam splitters) rather than by physical beam splitters, which mirroring surfaces can for example be designed as classical mirrors or as total-reflection prism surfaces. Here, the mirror surfaces for decoupling the co-observer beam path are arranged such that they do not protrude into the partial beam paths of the main observer. Such protrusion would lead to so-called vignetting, that is to say a decrease in light in the main observer beam path. Therefore, vignetting should be avoided where possible. Operating microscopes with mirrors instead of with physical beam splitters for decoupling the co-observer beam path are described in, for example, US 2008/0239473 A1, in DE 10 2004 049 368 A1 and in EP 1 089 107 A1.
Furthermore, it is desirable, or even necessary, for the co-observer also to be able to view the red reflex in ophthalmological operating microscopes. Since the generation of the red reflex presupposes that the angle between the observation beam path and the illumination beam path is as small as possible, the arrangement of the observation pupils in the objective plane of the main objective must be selected such that both the angle between the illumination beam path and the observation beam path of the main observer, and the angle between the illumination beam path and the observation beam path of the co-observer is as small as possible. It is for this reason that use is often made of a pupil arrangement in which the two pupils of the stereoscopic co-observer beam path are arranged, twisted by 90°, between the two pupils of the stereoscopic main observer beam path. By way of example, such arrangements are described in EP 1 089 107 A1 and in U.S. Pat. No. 5,898,518. Here, the co-observer tube can typically be offset by 180°, in order to be able suitably to select the position of the co-observer for an operation on the right or left eye. Such displaceability can be obtained by a rotation of the co-observer tube, as described in EP 1 089 107 A1 and in U.S. Pat. No. 5,898,518. Alternatively, it is also possible for provision to be made for openings in the main microscope for inserting the co-observer tube therein on two opposing sides of the main microscope, as mentioned in, for example, U.S. Pat. No. 5,898,518.
However, in general it is desirable to be able to provide the orientation of the co-observer tube relative to the main observer tube not only in two fixed positions, but to be able to set the orientation in a selective fashion over a range. However, care has to be taken therein for vignetting to be avoided as far as possible in order to prevent noticeable light loss from being brought about for the main observer. At the same time, the co-observer should also, where possible, be provided with the option of being able to view red reflex.
Therefore, it is an object of the present invention to provide an operating microscope that satisfies the aforementioned requirements. It is a further object of the present invention to provide a method for pivoting a co-observer tube in an operating microscope, by means of which the aforementioned requirements can be satisfied.